Device for impressing signaling currents on electrical powerdistributing lines



May 6, 1930. M. CHIROL 1,757,900

DEVICE FOR IMPRESSING SIGNALING CURRENTS v ON ELECTRICAL POWERDISTRIBUTING LINES Filed Oct. 7, 1927 lnvenl'br M U/LimZ Patented May 6,1930 UNITED STATES PATENT OFFICE MAURICE CHIROL, OF PARIS, FRANCE,ASSIGNORTO COMPAGNIE POUR LA FABRICA- TION DES COMPT EURS ET MATERIELDUSINES A, GAZ, OF MONTROUGE, SEINE, FRANCE, A JOINT-STOCK COMPANY OFFRANCE DEVICE FOR IMPRESSING SIGNALING CURRENTS ON ELECTRICAL FOWERDISTRIBUTING LINES Application filed October 7, 1927, Serial No.224,753, and in France October 26, 1926.

The present invention relates to a device enabling high frequencysignaling currents to be superimposed on currents of industrial or lowfrequency supplied by electrical distributing systems.

low frequency current nor its dangerous effects are ever entirelyannulled. In certain systems, however, and in certain cases, it ispossible almost to annul the efiect of the power supply current by usingshunts which resonate at the frequency of the power supply current, but,owing to the low frequency of said current, large condensers mustnecessarily be used.

The present invention enables the effect of 25 the supply current on'thesignaling apparatus proper to be practically eliminated, by making useof devicestermed chokes which are tuned to the frequency of thesignaling current.

According to a characteristic feature of the present invention, twoelectro-magnetic circuits are interposed between the signaling currentemitting apparatus and the supply lines on which such signaling currentis to be superimposed, such circuits being so arranged as to let throughthe low frequency supply current in order to produce two opposed fluxesof zero resultant whereby the effect of said current on the signalingapparatus is practically eliminated, whilst the signaling current isallowed to pass through one of said circuits which superimposes it onthe distributing line, the other of said circuits having a choke device,which prevents the signaling current from flowing therethrough.

According to a further characteristic of the present invention, the twocircuits above mentioned are coupled to the distributing line and signalemitting apparatus by means of'two transformers the primary windings ofwhich are respectively inserted in the distributing line and signalemitting apparatus circuits, Whilst the two secondaries of saidtransformers each comprise a coil divided into two sections which arerespectively inserted in the aforesaid electro magnetic circults.

The two sections of the secondary coil of the transformer which couplesthe signaling current'emitting apparatus'to said two electro-magneticcircuits are oppositely wound so that, when the power supply currentflows through them equal and opposite fluxeswill be created whereby saidpower supply current will'have no efiect on the primary windingof thetransformer coupling said electromagnetic circuits and thesignalingapparatus together.

According to 'another characteristic of the invention, the choke deviceinserted in one of said -electro=magneticcircuits consists inaninductanc'e and a capacity tuned to enter into resonance at thefrequency ofthe signaling current and mounted in parallel in saidelectro ma'gnetic circuit.

According to a further form of embodiment of the present invention inorder to eliminate more effectively the effect ofthe power supplycurrent on the signaling apparatus and in orderto impress the signalingcurrent more easily on the distributing line,

an inductance and a capacity tuned to enter into resonance'at thesignaling frequency are mounted in series in the electro-magneticcircuit which does not include the choke arrangement, said inductancebeing identical to that of the choke device.

According to a final characteristic of the present invention enablingsignaling currents to be impressed across two wires of adistributingline at difierent potentials, the distribution line is coupled to theelectro-magnetic circuits above mentioned through a shunt entering intoresonance at thesignaling current frequency and having a high impedancetothe low frequency power supply current.

The invention'will be more readily understood from the descriptionabout'to be made A 4! thereof with reference to the accompanying drawingin which:

Fig. 1 shows a circuit arrangement for impressing signaling currents ona conductor of a low frequency electrical power distributing line.

Fig. 2 shows a circuit arrangement for impressing signaling currentsacross two conductors under potential difference of a low frequencyelectrical power distributing line.

Fig. 3 shows a modified form of the circuit of Fig. 2.

Fig. 1 shows a modified form of the circuit of Fig. 1.

Turning to Fig. 1, 1 is a conductor of an electrical distributing systemthrough which a current 1 flows; 18 comprehensively designates a currenttransformer of which 19 is the primary winning whilst the secondarywinding is in two coil sections 5 and 7. The primary winding 19 ismounted in series with the conductor 1; comprehensively denotes atransformer the primary 13 of which is connected to an alternator 15 forproducing the signaling current which is to be impressed on theconductor 1. The secondary of the transformer 10 is in two sections 11and 12 which are oppositely wound and respectively connected to thecoils 5 and 7. 1 1 is the magnetic circuit of the transformer 10; 16 and17 are respectively a capacity and an inductance mounted in parallel andtuned to enter into resonance at the frequency of the current generatedby the alternator 15.

This device operates as follows:

Under normal circumstances, the current 1 produces in the circuits 5, 11and 7, 12, 16, 17 two currents of slightly different magnitudes owing tothe presence of the inductance 17 in the circuit 7, 12. These currentsproduce in turn two fluxes of opposite sign in the magnetic circuit 14:.The windings 11 and 12 are suitably designed so that said fluxes shallbe practically equal; consequently the resulting field in the magneticcircuit 1 1 is practically nil and no current is produced in the winding13.

In order to emit signaling current, the alternator 15, connected to thewinding 13, is started up. The current generated by said alternator, notbeing able to flow in the circuit 12, 7, 16, 17 owing to the chokeeffect of the circuit 16, 17, only flows through the circuit 11, 5 andinduces in the winding 19 a current of the signaling frequency which issuperimposed on the current 1.

Thus the current 1 of industrial frequency does not flow through thesignaling current alternator 15, and the signaling current only flows inone of the electro-magnetic circuits which impresses it in the supplyline 1.

I11 Figs. 2 and 3, an application of the present invention tosuperimposing a signaling current across two conductors of an electricaldistribution system has been shown. In

Fig. 2, 20 is a generator of current of industrial frequency, 21 and 22are two power distributing cables respectively connected to theterminals of the generator 20; 23 designates comprehensively atransformer the primary winding 24 of which is in series with theprimary winding 25 of a second transformer comprehensively denoted by29; the transformer 23 is the equivalent of the transformer 18 ofFig. 1. The secondary winding 26 of the transformer 29 is in series withan inductance 28 and a condenser 27. The condenser 27 and the inductance28 are tuned with the leakage inductance of the transformer 29 in suchmanner that this latter has the minimum impedance at the high frequencyof the current generated by the alternator 15. It has however a highimpedance at the low frequency of the supply current generated by thealternator 20.

The device then operates as follows:

The potential difference between the cables 21 and 22 set up by thegenerator 20 is prac tically nil between the ends of the winding 24-,whilst it is practically a maximum between the ends of the winding 25since the impedance of the latter has been purposely made high for thelow frequency of the current generated by 20.

When the alternator 15 emits current of high frequency to which the tworesonance circuits 16, 17 and 26, 27, 28 have been respectively tuned,the potential drop of such current is practically maximum between theends of the winding 24 and nil between the ends of the winding 25. Theconsequence is that the high frequency current is easily impressedacross the cables 21 and 22 whilst the current generated by thealternator 20 has no effect on the alternator 15.

In Fig. 3 the transformer 29 of Fig. 2 has been replaced by a condenser30. This condenser is tuned with the primary coil 24 of the transformer23 so that the impedance of the circuit 24, 30 shall be a minimum forthe high frequency current produced by the alternator 15. Moreover thepotential difference across the ends of the coil 24 due to the flow ofthe low frequency power supply current is practically nil as previouslyexplained, whilst the potential difference across the terminals of thecondenser 30 is then a maximum. In other respects, this device operatesin similar manner to that of Fig. 2.

In Fig. 4 has been illustrated an improvement on the circuit arrangementof Fig. 1. In the arrangement of Fig. 1, the low frequency currentflowing in the circuit 7, 16, 17, 12 must be out of phase with the lowfrequency current flowing in the circuit 5, 11, owing to the presence ofthe choke device 16, 17, so that the fluxes produced by the coils 11 and12 can not exactly balance, from which it ensues that a resultant fieldmust necessarily exist in ducing low frequency current in the winding 13and hence affecting the signaling current alternator 15. Furthermore,the points of juncture of the coils, 5, 7 and 11, 12 are not absolutelyat equipotential and a low frequency current will flow in theirconnecting wire. The arrangement illustrated in Fig. i remedies thedefects by the provision in the circuit 5, 11 of an inductance 31,identical to the inductance 17 of the circuit 7 16, 17, 12, whilst, inseries with said inductance 31, is mounted a condenser 32 in the wire33. Said condenser 32 is so designed as to enter into resonance with theinductance 31 and the leakage inductances of the windings 5 and 7 at thefrequency of the signaling current.

This device operates as follows:

The low frequency current flows through the cable 1 and the winding 19;it induces in the windings 5 and 7 a current which flows through thecircuit 7, 17 12, 11, 31, for the current in the condenser 16 ispractically negligible. Likewise practically no low frequency currentflows through the condenser 32 which is now connected across two pointsat practically the same potential owing to the presence of theinductance 31. In consequence, the windings 11 and 12 being oppositelywound create two equal and opposite fluxes. The resultant of such fluxesis nil and hence no low frequency current fiows through the winding 13.

lVhen a current of signaling frequency is emitted, such current flowsthrough the winding 13 which produces a flux in the magnetic 1- circuit14; this flux in turn produces in the windings 11 and 12 respectivelytwo electromotive forces which are equal and opposite. The electromotiveforce produced in the winding 12 cannot give rise to a current due tothe choke circuit 16, 17. On the other hand, the electromotive forceproduced in the winding 11 easily gives rise to a current in the circuit31, 5, 32 owing to the fact that the condenser 32 is in resonance withthe inductance 31 and the leakage lnductances of the windings 5 and11-,at the signaling current frequency.

The arrangement that has just been described can be used forsuperimposing signaling currents on electric supply lines either inseries with the low frequency power supply current, or in parallel withthe same.

I claim:

1. Device for superimposing currents of signaling frequency on a lowfrequency electric supply system comprising, in combina tion, a lowfrequency electric supply system, signaling current emitting apparatus,two electro-magnetic circuits inductively coupling said low frequencysupply circuit and said signaling current apparatus together and bothadapted to let through said low frequency current, means included insaid electro-magnetic circuits for causing said low J frequency currentto produce two opposed and practically equal fluxes whereby practicallyno low frequency current is induced in said signaling current emittingapparatus, choke means included in one of said electro-magnetic circuitsfor preventing the flow of current of signaling frequency therethroughand means in the other of said two electro-magnetic systems forfacilitating the flow of current of signaling frequency therein.

2. Device for superimposing currents of signaling frequency on a lowfrequency electric supply system comprising, in combination,-a lowfrequency electric supply system, a signaling current emittingapparatus, two electro-magnetic circuits inductively coupling said lowfrequency supply circuit and said signaling current apparatus togetherand both adapted to let through said low frequency current, meansincluded in said electro1nagnetic circuits for causing said lowfrequency current to produce two opposed and practically equal fluxeswhereby practically no low frequency current is induced in saidsignaling current emitting apparatus, choke means included in one ofsaid electromagnetic circuits for preventing the flow of current ofsignaling frequency therethrough and means in the other of said twoelectromagnetic systems for eliminating the phase displacement of thelow frequency currents flowing in said two electro-magnetic circuitsintroduced by said choke means.

3. Device for superimposing currents of signaling frequency on a lowfrequency electric supply system comprising, in combination, a lowfrequency electric supply system, signaling current emitting apparatus,two electrounagnetic circuits inductively coupling said low frequencysupply circuit and said signaling current apparatus together and bothadapted to let through said low frequency current, means included insaid electro-magnetic circuits for causing said low frequency current toproduce two opposed and practically equal fluxes whereby practically nolow frequency current is induced in said signaling current emittingapparatus, choke means included in one of said electro-magnetic circuitsfor preventing the flow of current of signaling frequency therethrough,and means in the otherv of said two electro-magnetic systems forconcomitantly facilitating the flow of current of signaling frequencytherein and eliminating the phase displacement of the low frequencycurrents flowing in said two electro-magnetic circuits introduced bysaid choke means.

l. Device for superimposing currents of signaling frequency on a lowfrequency elec tric supply system comprising, in combination, a lowfrequency electric supply circuit, signaling current emitting apparatus,two

electro-magnetic circuits inductively conpling said low frequency supplycircuit and said signaling current apparatus together and both adaptedto let through said low frequency current, means included in saidelectro-niagnetic circuits for causing said low frequency current toproduce two opposed and practically equal fluxes whereby practially nolow frequency current is induced in said signaling current emittingapparatus, twoidentical inductances respectivelymounted in saidelectro-inagnetic circuits, two capacities respectively mounted inparallel and series with said inductances in said electromagneticcircuits and adapted to enter into resonance With said inductances atthe frequency of said signaling current, said parallel and seriescondenser and capacity arrangements respectively preventing andassisting the flow of signaling current through their respectiveelectro-magnetic circuits.

MAURICE OHIROL.

